diff --git a/addons/promex/service-prometheus.c b/addons/promex/service-prometheus.c
index 06eb1eea9..48bf1602d 100644
--- a/addons/promex/service-prometheus.c
+++ b/addons/promex/service-prometheus.c
@@ -1509,8 +1509,20 @@ static void promex_appctx_handle_io(struct appctx *appctx)
 			/* fall through */
 
 		case PROMEX_ST_DONE:
-			/* no more data are expected. Don't add TLR because mux-h1 will take care of it */
-			res_htx->flags |= HTX_FL_EOM;
+			/* no more data are expected. If the response buffer is
+			 * empty, be sure to add something (EOT block in this
+			 * case) to have something to send. It is important to
+			 * be sure the EOM flags will be handled by the
+			 * endpoint.
+			 */
+			if (htx_is_empty(res_htx)) {
+				if (!htx_add_endof(res_htx, HTX_BLK_EOT)) {
+					si_rx_room_blk(si);
+					goto out;
+				}
+				channel_add_input(res, 1);
+			}
+		        res_htx->flags |= HTX_FL_EOM;
 			si->cs->flags |= CS_FL_EOI;
 			res->flags |= CF_EOI;
 			appctx->st0 = PROMEX_ST_END;